Method of making polished annealed stainless steels



. mately that which they had before the treat- Patented Sept. 22, 1931 um'rso s'r ss :PATENT OFFICE FRANCIS LOCKE, OIL NORTH ATTLEBOBO, MASSACHUSETTS, ASBIGNOR TO J. D. CROSBY COMPANY, OF PAWTUOKET, RHODE ISLAND, A CORPORATION Oil? NEW YORK 0! m6 POLISHED mum STAINLESS STEELS Roi I i u The object of m invention is to provide a stainless steel an iron and the rocess of making the same. Whenever stainless steel or iron (for the purposes of this case called 8 stainless steel) has been heated-either to anneal, harden, or otherwise heat treat, it has been found that a discoloration or oxide-is deposited on the surface which is removed with difiiculty, and if the steel has a good 10 finish before the heating treatment, this finish is destroyed by the attempts to remove the scale. My invention eliminates this difliculty and by my rocess, described below, stainless steels are eated in such a manner 15 that they are discolored evenly and lightly and subsequently are restored to a bright, clean, oxide free, condition, free from pits, or other surface defects, such as would occur if the ordinary scale removing processes were employed, and with a finish approximent. This finish is bettered further by light buffing.

This and other objects are accomplished by my invention, one embodiment of which is hereinafter more particularly set forth.

In the preferred embodiment of my invention, stainless steel of a suitable kind and character is passed cold through a series of rollers. the finishing rollers having highly polished surfaces so that after the last pass the sheet of metal emerges in' a highly polished condition. This steel is then in the rollers. that it cannot be passed through dies or given similar treatment. If it be annealed inthe ordinary way. the surfaces will be oxidized to such an extent that the high polish due to the rolling cannot be restored; Mv invention overcomes all difficulties and results in a product asabove set forth.

My improved process and product will now be described in detail.

The raw maten'wl The raw material may be hot rolled rods which must be clean, free from scale, black deposit stains, etc., and for convenience, these 7 rods maybe annealed before rolling, although such a hard condition, due to the action of per minute.

Application filed June 18, 1829. Serial No. 871,980.

this annealing is not essential. It is, however, desirable.

Rolling Amwaling The steel, in long strips, is drawn through an annealing furnaceand kept at the proper temperature while in the furnace, say substantially 1400 F., the exact temperature derom the furnace, this steel passes into a long cooling chamber, and out into the open air.

ending on the exact nature of the steel.

While being passed through the furnace and cooling chamber, the strip must not have any contact with any substance except a relatively movable substance, but must pass, with a continuous movement, over continuously moving rollers, running with a peripheral velocity equal to the velocity of the strip, as

nearly as may be. When the end of one strip is reached, another is secured to it,

preferably by spot welding, and this follows the first strip through the furnace and cooling chamber and this is continued while the apparatus is functioning. The velocity of and cooling chamber. is-substantially 10 feet The fu maintained in the cooling chamber until near the exit end and so the strip is kept out of contact with air until near the end of the cooling chamber. The furnace atmosphere is such that there is a slight oxidizing effect .the strip, when passing through the furnace rnace atmosphere is on the strip. This is important because itLis, exceedingly desirable that no deep or dificut scale be allowed to accumulate on the strip. =Whatever does accumulate can be readily removed and is readily removed the next step of the process.

Cleaning The scale or oxide on the steel from the annealing is removed as follows:

The steel is run continuously throu h a bath of substantially.10% sulphuric aci and while passing through this bath an electric current is passed through the strip, the cur-- rent being a direct current of about 6 volts and the strip is the positive pole and the strip passes adjacent to metal plates which constitute the negative pole. These negative plates both lie over and below the strip. The combination of acid and electricity loosen the scale so that it is easily removed and brushed ofibefore and after a bath through which the strip is passed. Thereafter-the strip is drawn through a tank with water, which rinses the strip and withdraws all acids from the same and thereafter the strip is dried suitable drying material. From this final drying the strip passes to a reel where it is allowed to accumulate. V

Inferior results may be obtained if an alternating current be employed.

It is not essentialthat sulphuric acid be a sulphate of copper solution. Sulphuric acid of the kind, character and strength above indicated has been found suitable for the purpose of this process." The strip The strip, when processed as above described, has a finish, which when bufied is changed to a hi h polish, like that of a mirror. This polis may be obtained by bufiing after the strip has been further processed by dies. This further processing would be impossible if the stri we're not'ln an annealed Egndition prior to eing passed through the With steels having an inferior initial finish, correspondingly inferior results are obtained although such finishes are superior to the prior art rolled finishes.

making the same", it is obvious that it is not restricted thereto but that it is broad enough to cover all products and'processes that come within the scope of the annexed claims.

neal'ed, stainless steel which consists iii rolling the stainless steel'un'til it has-tlie desired an annealin furnaceand the same through 7 t oxide or sea e on the same depositing a lig by being passed through sawdust or other.

and thereafter removing this oxide or scale aaaaooa 'by passin this steel through an acid bath, energized electricity, the steel being the positive po e and thereafter washing or cleaning the loose scale-resulting from the acid bath treatment.

2. The process of making a bright, clean, heat treated, stainless steel with its scale removed which consists in heating the steel in an atmos here which will oxidize it slightly and eve y and then removing this oxide or scale by passin this steel through an acid bath, energized y electricity, the steel being the positive pole, and thereafter washing or cleaning the loose scale resulting from the acid bath treatment. 7

In testimony whereof, I have hereunto set my hand this 14th day of June, 1929.

. FRANCIS LOGK'E.

used, because any equivalent acid solution? may be used, ore solution of salts, such as While I have shown and described one ein-l bodiment of my invention and the process of Having thus described iny invention, what Iclaim-is: ,1. The process of'making apolished, an-

dimensions and polish 'and' then passing 

